Highly efficient excitation and detection of whispering gallery modes in a dye-doped microsphere using a microstructured optical fiber

A technique for the excitation of whispering gallery modes (WGMs) has been demonstrated using a dye-doped microsphere positioned onto the tip of a suspended core microstructured optical fiber. With this configuration, we have shown that both the excitation and collection efficiency of the WGMs modulated fluorescence spectra of the dye are greatly improved compared to a more conventional excitation scheme; an overall efficiency increase by a factor of 200 is demonstrated. It is also shown that positioning the resonator onto the fiber tip does not impact its sensitivity, providing a compact and robust architecture for applications such as localized in-vivo/vitro biosensing.